Water-soluble polymeric films are commonly used as packaging materials to simplify dispersing, pouring, dissolving and dosing of a material to be delivered. For example, packets made from water-soluble film are commonly used to package household care compositions, e.g., a pouch containing a laundry or dish detergent. A consumer can directly add the pouch to a mixing vessel, such as a bucket, sink or washing machine. Advantageously, this provides for accurate dosing while eliminating the need for the consumer to measure the composition. The pouch may also reduce mess that would be associated with dispensing a similar composition from a vessel, such as pouring a liquid laundry detergent from a bottle. In sum, soluble polymeric film packets containing pre-measured agents provide for convenience of consumer use in a variety of applications.
Some water-soluble polymeric films that are used to make packets will incompletely dissolve during the wash cycle, leaving film residue on items within the wash. Such problems may particularly arise when the pouch is used under stressed wash conditions, such as when the pouch is used in cold water, i.e. water at as low as 5° C. Notably, environmental concerns and energy cost are driving consumer desire for utilizing colder wash water.
Alternatively, water-soluble polymeric films that completely dissolve in cold water can be too sensitive to moisture and humidity to make pouches for the consumer market. For example, high humidity or water droplets from handling of the pouches with wet hands can cause the soluble packets to stick together and/or dissolve through the packets and cause leakage of pouch contents.
Packets made from some films comprising polyvinyl alcohol polymers have addressed the aforementioned issues with some success. However, the cold water solubility of some polyvinyl alcohol films may decrease when they are in contact with certain detergent compositions. Without being bound by theory, it is believed that the film becomes less soluble due to chemical interactions between the film and the composition inside the pouch. Consequently, as they age, the packets may incompletely dissolve during a cold wash cycle, and may in turn leave film residue on items within the wash.
Packets made from water-soluble films comprising polymers other than polyvinyl alcohol polymers may fail to successfully address each the aforementioned problems. For example, a polymeric film comprising starch and/or cellulosics may provide good water-drop resistance. Yet, to achieve good cold water solubility, such a film may have to be so thin that its mechanical properties, including those relating to processability, are compromised. Moreover, films comprising starch and/or cellulosics are not nearly as readily processable given their relative lack of mechanical stretchability or elongation as compared to films of like thickness comprising polyvinyl alcohol polymers.
No commercially available film currently performs adequately in these three situations. Thus, there remains a need for packets comprising water-soluble films having the desired characteristics of good cold water-solubility, water-drop resistance, and mechanical properties including, but not limited to, good processability.